1. Field of Invention
The present disclosure relates to a cementing tool having a seal on an outer surface that is formed by selectively aligning seal members along a circumference of the tool.
2. Description of Prior Art
Hydrocarbons that are produced from subterranean formations typically flow from the formation to surface via wellbores that are drilled from surface and intersect the formation; where casing often lines the wellbores. The casing is usually bonded to the inner surface of the wellbore with a cement that is injected into an annulus that is between the casing and wellbore. In addition to anchoring the casing within the wellbore, the cement also isolates adjacent zones within the formation from one another. Zonal isolation is especially useful when adjacent zones have different types of entrained fluids, i.e. oil or gas hydrocarbon versus non-hydrocarbon water. Without the cement isolating these adjacent zones, the different fluids could become mixed, which requires subsequent separation, or can reduce the hydrocarbon producing potential of the wellbore. The cement also prevents hydrocarbon fluid from flowing uphole from a hydrocarbon producing zone and to the surface. Without the cement, or in instances when cement has failed, hydrocarbons are known to migrate to surface.
A common method for injecting the cement into the annulus between the casing and wellbore sidewall involves pumping cement inside the casing, and then forcing the cement to the casing bottom, where the cement then flows back up into the annulus. How much cement is injected is estimated based on the annulus volume in which the cement is being injected. To force the cement upward in the annulus, a plug is landed on top of the cement column, and pressurized fluid is injected into the casing to push the plug downward inside the casing. A cement shoe is often provided at the lowermost end of the casing, and which the plug latches to when it reaches the casing bottom. The plug prevents the cement from flowing from the annulus and into the casing. In some deep wells, such as those exceeding 15,000 feet in depth, surface pressures required to force the cement up the entire annulus, particularly with a very heavy cement slurry, may exceed what is possible or practical to handle without risking the failure of surface or downhole equipment. Also, some wellbores have sections that cannot withstand the hydrostatic pressures necessary to displace a single column of cement in the annulus, and can allow an out-flux of fluid when subjected to these pressures—a condition commonly referred to as lost circulation. To avoid these high pressure problems, cement is sometimes injected in stages into axial sections of the annulus.